1. Field of the Invention
The present invention relates to a slide fastener stringer of the airtight or watertight type.
2. Prior Art
A known form of watertight slide fastener stringer is shown in U.S. Pat. No. 2,910,754, issued Nov. 3, 1959. With this type of arrangement, a pair of coupling element halves one on each side of a stringer tape are interconnected and attached to the tape only by an integral connector remote from their coupling heads that project beyond a thickened or beaded edge of the tape. When subjected to a severe thrust applied perpendicularly to the plane of the slide fastener, the interdigitating coupling heads tend to be yielded in a direction away from the stringer tapes, and the thickened edges of the tapes could be displaced out of sealing contact with each other. Under heavier load conditions, the coupling elements are liable to be ruptured because of their relatively weak strength of attachment to the tapes. The prior sealing slide fastener is therefore unreliable in applications in which it will undergo a great amount of pressure.